In-plane switching display device having common electrode overlapping channel forming region, and double gate TFT

Abstract

A method of forming a storage capacitor in an IPS liquid crystal display device is proposed, and a technique of forming a pixel region having a high aperture ratio is provided. An anodic oxidation process at an applied voltage/voltage supply time ratio of 11 V/min is performed for insulating films used in each circuit of an electro-optical device, typically an IPS method LCD, in particular for the surface of a common electrode formed on a resin film. The amount of formation of the extra anodic oxide film can be reduced by covering with an anodic oxide film, and a liquid crystal display device with high reliability and having an electrode with superior adhesion can be manufactured.

1. An In-Plane Switching display device comprising:
 a pair of substrates, 
 at least one thin film transistor formed over one of the pair of substrates; 
 an insulating layer formed over the thin film transistor; 
 a common electrode formed on the insulating layer; 
 a pixel electrode formed on the insulating layer and electrically connected to the thin film transistor via a contact hole in the insulating layer; and 
 a capacitor electrically connected to the pixel electrode; 
 wherein the thin film transistor comprises a semiconductor island, a gate insulating layer on the semiconductor island, and first and second gate electrodes on the gate insulating layer, and 
 wherein the common electrode overlaps the semiconductor island. 
 
   
   
     2. The In-Plane Switching display device according to  claim 1 , further comprising a liquid crystal layer located between the pair of substrates. 
   
   
     3. The In-Plane Switching display device according to  claim 1 , said the semiconductor island has at least first and second channel regions adjacent to the first and the second gate electrodes, a first impurity region located adjacent to the first channel region, a second impurity region located between the first and the second channel regions, and a third impurity region located adjacent to the second channel region. 
   
   
     4. The In-Plane Switching display device according to  claim 1 , wherein the In-Plane Switching display device comprises at least one electric equipment selected from the group consisting of a video camera, a digital camera, a projector, a goggle type display, a car navigation system, a personal computer, and a portable information terminal. 
   
   
     5. The In-Plane Switching display device according to  claim 1 , wherein the common electrode and the pixel electrode have a zigzag shape. 
   
   
     6. The In-Plane Switching display device according to  claim 1 , further comprising a color filter located over the pixel electrode. 
   
   
     7. An In-Plane Switching display device comprising:
 a semiconductor film formed over a substrate, said semiconductor film having at least a channel forming region, a source region, and a drain region; 
 a gate electrode adjacent to the semiconductor film with a gate insulating film interposed therebetween; 
 source and drain electrodes connected to the source and drain regions, respectively; 
 an insulating layer formed over the source and drain electrodes; 
 a common electrode formed on the insulating layer; 
 a pixel electrode formed on the insulating layer and electrically connected to the drain electrode via a contact hole in the insulating layer; and 
 a capacitor electrically connected to the pixel electrode; 
 wherein the thin film transistor is double gate structure thin film transistor, 
 wherein an electric field parallel to the face of the substrates is applied between the pixel electrode and the common electrode, and 
 wherein the common electrode overlaps the semiconductor film. 
 
   
   
     8. The In-Plane Switching display device according to  claim 7 , wherein the insulating layer comprises an organic resin material. 
   
   
     9. The In-Plane Switching display device according to  claim 7 , further comprising a liquid crystal layer located over the pixel electrode. 
   
   
     10. The In-Plane Switching display device according to  claim 7 , wherein the In-Plane Switching display device comprises at least one electric equipment selected form the group consisting of a video camera, a digital camera, a projector, a goggle type display, a car navigation system, a personal computer, and a portable information terminal. 
   
   
     11. The In-Plane Switching display device according to  claim 7 , wherein the common electrode and the pixel electrode have a zigzag shape. 
   
   
     12. The In-Plane Switching display device according to  claim 7 , further comprising a color filter located over the pixel electrode. 
   
   
     13. An In-Plane Switching display device comprising:
 a pair of substrates, 
 at least one thin film transistor formed over one of the pair of substrates; 
 an insulating layer formed over the thin film transistor; 
 a common electrode formed on the insulating layer; 
 a pixel electrode formed on the insulating layer and electrically connected to the thin film transistor via a contact hole in the insulating layer; and 
 a capacitor electrically connected to the pixel electrode; 
 wherein the thin film transistor comprises a semiconductor island, a gate insulating layer on the semiconductor island, and first and second gate electrodes on the gate insulating layers 
 wherein the pair of the substrates is surrounded by a sealing material, and spacers are formed in the region in which the sealing material is formed, and 
 wherein the common electrode overlaps the semiconductor island. 
 
   
   
     14. The In-Plane Switching display device according to  claim 13 , further comprising a color filter located over the pixel electrode.